From 167012daf75436208bcf275164792f3ec06ee56c Mon Sep 17 00:00:00 2001
From: John MacFarlane <jgm@berkeley.edu>
Date: Mon, 10 Sep 2012 14:35:21 -0700
Subject: Export 'nested' in Parsing.

---
 src/Text/Pandoc/Parsing.hs | 13 +++++++++++++
 1 file changed, 13 insertions(+)

(limited to 'src/Text/Pandoc/Parsing.hs')

diff --git a/src/Text/Pandoc/Parsing.hs b/src/Text/Pandoc/Parsing.hs
index d4a1afbec..bee96be82 100644
--- a/src/Text/Pandoc/Parsing.hs
+++ b/src/Text/Pandoc/Parsing.hs
@@ -82,6 +82,7 @@ module Text.Pandoc.Parsing ( (>>~),
                              ellipses,
                              apostrophe,
                              dash,
+                             nested,
                              macro,
                              applyMacros',
                              Parser,
@@ -925,6 +926,18 @@ emDashOld = do
   try (charOrRef "\8212\151") <|> (try $ string "--" >> optional (char '-') >> return '-')
   return (Str "\8212")
 
+-- This is used to prevent exponential blowups for things like:
+-- a**a*a**a*a**a*a**a*a**a*a**a*a**
+nested :: Parser s ParserState a
+       -> Parser s ParserState a
+nested p = do
+  nestlevel <- stateMaxNestingLevel `fmap` getState
+  guard $ nestlevel > 0
+  updateState $ \st -> st{ stateMaxNestingLevel = stateMaxNestingLevel st - 1 }
+  res <- p
+  updateState $ \st -> st{ stateMaxNestingLevel = nestlevel }
+  return res
+
 --
 -- Macros
 --
-- 
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